OF THE BRAIN, ETC. 13 



which the circulation was maintained by artificial 

 respiration, cooled more rapidly than the dead 

 rabbit, but the difference was more perceptible 

 in the thorax than in the rectum. This is what 

 might have been expected, if the production of 

 animal heat be not immediately dependent on 

 respiration, since the cold air by which the lungs 

 were inflated, must necessarily have abstracted a 

 certain quantity of heat from the whole body, 

 and a still larger quantity from the parts with 

 which it came into actual contact. 



Still, it was plain that some animal heat might 

 have been generated, though so small in quantity 

 as not to counterbalance the cooling powers of 

 the air thrown into the lungs. It is difficult or 

 impossible, to ascertain with perfect accuracy, 

 what effect cold air thrown into the lungs would 

 have on the temperature of an animal under the 

 circumstances of the last experiment, indepen- 

 dently of any chemical action on the blood : 

 since, if no chemical changes were produced, the 

 circulation could not be maintained, and if the 

 circulation ceased, the cooling properties of the 

 air must be more confined to the thorax, and 

 not communicated in an equal degree to the 

 more distant parts. The following experiment, 

 however, was instituted, as likely to afford a 

 nearer approximation to the truth, than any 

 other that could be devised. 



EXPERIMENT VIII. 



I procured. two rabbits of the same /^^^^ 

 colour. The temperature of the room was 64. 



